Fuel injectors



June 19, 1962 D. R. CARLISLE 3,039,701

FUEL INJECTORS Filed Aug. 4, 1960 Inventor Attorneys United States Patent l 3,039,701 FUEL INJECTORS Denis Richard Carlisle, Risley, England, assignor to Rolls-Royce Limited, Derby, England Filed Aug. 4, 1960, Ser. No. 47,414 Claims priority, application Great Britain Aug. 8, 1959 2 Claims. (Cl. 239-419) This invention relates to fuel injectors for use in continuous combustion internal combustion engines, such as gas turbine engines, and is particularly concerned with injectors having pilot and main fuel sprays. Fuel injectors of this type are usually known as duplex burners.

According to the present invention a duplex fuel injector comprises a central pilot fuel injection nozzle, a main fuel injection nozzle surrounding the pilot fuel nozzle and means outside the pilot nozzle but within the main nozzle for dividing a proportion of the pilot fuel spray into separate circumferentially-spaced-apart streams of fuel spray, and for deflecting the remaining proportion of pilot fuel spray axially downstream with a narrow spray angle.

The main fuel spray is preferably ejected so that a portion of it impinges on the streams of pilot fuel spray and the remainder passes between the said streams.

Preferably the means for dividing the pilot fuel spray into separate streams comprises an open ended cowling surrounding the outlet of the pilot fuel nozzle and extending downstream therefrom, the cowling being provided with circumferentially-spaced-apart apertures through which a proportion of the pilot fuel spray passes, the remaining proportion of pilot fuel spray being deflected by the cowling.

The cowling preferably passes within the main fuel injection nozzle and terminates at its downstream end in the plane of the outlet of the main fuel nozzle.

The main fuel spray preferably has a conical spray angle greater than the pilot spray angle so that when the main fuel spray is well developed it is substantially unaffected by the pilot fuel spray.

In a preferred arrangement the apertures provided in the cowling are in the form of rectangular slots open at their downstream end.

By dividing the pilot fuel spray into separate streams the atomization of the fuel is not seriously impaired but the distribution of the fuel is greatly improved for igni tion and continuous burning at low fuel flows. When the main fuel flow is low the pilot spray assists in atomization of the main fuel and distributes it in a similar pattern to that obtained on pilot flow only. At higher main fuel flows the main spray angle becomes strongly developed and the elfect of the separate streams of pilot spray becomes lessened and the combined pilot and main sprays produces a normal conical spray. The cowling is cooled by the main fuel flow which also prevents the build up of carbon on the Cowling.

One embodiment of the invention will now be described with reference to the drawings accompanying the provisional specification in which:

FIGURE 1 is an axial section through a fuel injector according to the invention; and

FIGURE 2 is a fragmentary end elevation of the fuel injector in the direction of arrow H shown in FIGURE 1.

3,039,701 Patented June 19, 1962 The fuel injector comprises a body portion 10, .a fuel transfer member 11, a pilot fuel atomizer 12, a main fuel atomizer 13 and a sleeve member 14 which secures the member 11 and fuel atomizers 12, 13 to the body portion 10.

The body portion 10 is provided with a passage 15 through which the main fuel supply flows and a passage 16 through which the pilot fuel supply flows. The passage 15 communicates wtih an annular manifold 17 formed in the end face of the body portion 10 and a series of axial passages 18 are provided in the transfer member 11. Each passage 18 communicates at one end with the manifold 17 and at its other end with an annular manifold 19 provided in the downstream face of the transfer member 11. Passageway 16 communicates with the open end of a drilling 20 and the member 11 is also provided with inclined passageways 21 which at one end are open to the interior of the drilling 20 and at their other end are open to the downstream face of the member 11.

The annular manifold 19 communicates with a series of passageways 22 provided in the pilot fuel atomizer 12 and the inclined passageways 21 communicate with an annular manifold 23. The manifold 23 is placed in communication with a pilot fuel swirl chamber 24 through a series of ports 25 which are arranged tangentially (not shown) to the wall of the chamber 24 so as to impart swirl to the fuel flowing therethrough. The downstream wall of the chamber 24 is provided with an orifice 26 whose outlet is surrounded by a cowl 27 having a number of circumferentially-spaced-apart open-ended apertures 28.

Passageways 22 provided in the pilot fuel atomizer 12 communicate with an annular manifold 29 provided in the main fuel atomizer 13 and a main fuel swirl chamber 30 is placed in communication with the manifold 29 by means of a series of tangentially (not shown) disposed ports 31.

The downstream wall of chamber 30 is provided with an orifice 32 into which extends the downstream endof the cowl 27.

In operation of the fuel injector the pilot fuel supply passes through the passageway 16 to the drilling 20 and then through the inclined passageways 21 to the interior of the manifold 23 fiom where it flows through the ports 25 into the swirl chamber 24. The pilot fuel then passes along the chamber 24 and is discharged through the orifice 26 in the form of a conical spray indicated at 33. The cone angle of the spray is such that a portion of the fuel impinges on the cowl 27 and the remainder passes through the apertures 28 so that the pilot fuel spray is divided into a number of separate circumferentially-spaced-apart streams as indicated at 34 in FIG- URE 2.

The main fuel supply passes through the passageway 15 to the manifold 17 and then flows through drillings 18, manifold 19 and drillings 22 to the manifold 29 from where it flows through the ports 31 into the swirl chamber 30. The main fuel then passes along the chamber 30 and is discharged through the orifice 32 in the form of a conical spray which during low main fuel flows impinges on the separate streams 34 of pilot fuel which assists in the distribution of the main fuel supply.

. main fuel at the higher fuel flows, also the flow of the main fuel over the cowl prevents it being burned and keeps it cool.

What I claim is:

1. A duplex fuel injector comprising a central pilot fuel injection nozzle having a discharge orifice, a main.

fuel injection nozzle surrounding the pilot fuel injection nozzle and having a discharge orifice positioned downstream of the orifice of said pilot fuel injection nozzle, an open ended cowling supported by and extending downstream from the end of the pilot fuel injection nozzle and terminatingrin a downstream end lying in a plane of the orifice of said main fuel injection nozzle, said cowling having an inside diameter greater than the diameter of the orifice of said pilot fuel injection nozzle and an outside diameterless than the diameter of the orifice of said main fuel injection nozzle, said cowling being provided with a plurality of circumferentially spaced apart apertures therethrough, all of said apertures having an open end at the downstream end of the cowling and having a closed end terminating downstream of the orifice of said pilot fuel injection nozzle whereby a proportion of pilot fuel spray passes through the apertures in said cowling and impinges on portions of fuel spray from the main fuel injection nozzle, the remaining proportion of pilot fuel spray being deflected axially downstream with a narrow spray angle.

2. A duplex fuel injector as claimed in claim 1 in which the apertures provided in said cowling are in the form of rectangular slots open at their downstream end.

References Cited in the file of this patent UNITED STATES PATENTS 1,472,486 Morse Oct. 30, 1923 1,934,837 Zulver Nov. =14, 1933 2,551,276 McMahan May 1, 1951 2,703,260 Olson et al. Mar. 1, 1955 FOREIGN PATENTS 166,341 Great Britain July 12, 1921 299,310 Switzerland June 15, 1954 1,188,927 France Mar. 16, 1959 

